July - January
Page on "Beat Monthly" magazine updated. So far, all full-page Vox adverts for 1963-1964. 1965 to follow.
A rolling series of updates to the site will be started this coming weekend.
Above, the Westrex factory (or at least what was to become the Westrex factory), 152 Coles Green Road, Dollis Hill, photographed in 1930. Picture from the britainfromabove website.
Westrex not only assembled AC30s but the first two hundred AC80/100s for Vox. Triumph assembled AC50s (and much else).
The main business of Westrex however was equipment for cinemas. The Pathescope Camera Works and Stoll Film Studios were close by.
Mullard BY100 rectifier diodes
The Mullard pricelist of August 1965 gives the price, among other things, of the Mullard BY100 rectifier diodes used in AC80/100s, AC50s, the "100W Amplifier", and the AC100 Mk2 - 11s 6d each in old money, and around £10 each today in relative terms. But Vox presumably had a better (wholesale) price.
"100W Amplifier" - zener diodes - updated
Above, close-up shots of a zener diode temporarily removed from a "100W Amplifier" (serial number in the 500s, though lacking its plate on the back panel). Made by "International Rectifier", 15v (part no. MZ15), and rated at 3/4W. Below a shot of an MZ14 zener (not used by Vox) with its original box:
Thanks to the experts in the vintage-radio.net forum for identifying the MV15 zener as being made by IR.
A design handbook for the zener diode was issued annually in the early 1960s by the International Rectifier Co. and is likely to have been available to the Burndept engineers. A subsiduary International Rectifier Co. Ltd factory was set up in Oxted, Surrey, in 1960.
The standard arrangement of zeners in the "100W Amplifier" is shown in the pic below ( AC100 serial no. 531):
The 20v zener extends across the width of the board; the 15v bridges two adjacent tags.
The scattered notes on this page relating to the "100W Amplifier" will be gathered together to form a dedicated page of their own.
The page on PA Speakers further updated.
The page on late AC100s built at Burndept in the summer of 1967 according to schematic OS/167 tidied up and updated.
Early Vox PA columns
Pictured below is the wiring schema of the earliest Vox PA columns - 1963-1964. The drivers in these units are 10" Elacs, sprayed Vox blue, impedance 16ohms.
Click for a larger image
The pairs of speakers could either be run from dedicated PA amps, or from those early AC50s and AC80/100s that had twin XLR sockets. To use the two 16ohm columns together, one would set the impedance of the amp to 8ohms.
Later, 4ohm Elacs, finished in a light silver hammertone, were used, wired in series, again for a total of 16ohms.
Click for a larger image
The PA Speakers page has been updated - further updates to follow.
More on the "100W Amplifier", June/July 1965
For the smoothing capacitor C15 in the fixed bias circuit of the "100W Amplifier", the schematic notes 0.25uf (an unusual value), 750v (an unusual rating). Hunts certainly made caps of these specifications, but evidently not in great numbers. The part actually used at the Burndept factory, however, was a blue/grey RadioSpares paper cap, 0.25uf, 1000v, well above spec., as in serial no. 531:
These came in packs of three, as in the pics below:
In later fixed bias amps - the AC100 Mk2 - one often finds RadioSpares mixed dialectic caps (polythene/foil) of 0.22uf, 600v. The change made little difference to the circuit operationally.
The zener diodes were made by Mullard - MZ20 (20v) and MZ15 (15v), clamping the bias at -35v.
A snippet on Woden transformers
In the autumn of 1964, Vox ordered from Woden a second batch of transformers - around sixty or so - for the AC80/100s then being assembled at the Westrex factory in north London. The date codes of the new units were "JV" and "KV" - September and October 1964. All had plain metal shrouds, unlike the previous batch, which had green. See the Woden page for details.
At the same time, Vox evidently placed an order for transformers for the AC50s destined for production at the Burndept factory in Erith. These also had plain metal tops and for the most part codes "JV" and "KV" too. Some chokes however are dated "HV" = August 1964. See the AC50 site for details - entry for 2nd July.
So far as can be determined, the new plain-topped AC80/100 transformers went into amps with black control panels - mainly within the serial number range c. 230-300, produced late 1964 / early 1965 - but probably with a few exceptions here and there.
The black panel amps were in some ways a "holding position" at Westrex - a short final burst of activity pending the transfer of production (possibly later than intended) to the Burndept factory, where runs of AC50s had newly been set in motion.
Notes on TCC Capacitors
As mentioned lower down on this page, the higher value axial capacitors in the "100W Amplifier" were green TCC "Micromites":
Pic. from the wonderful Mullard Magic website. Note the statement of "Peak Working" and "Surge" voltages.
The caps in question, as marked on the schematic (for which, see lower down this page), are:
|C1||8uf, preamp main filter (but 16uf always fitted in practice)|
|C3, C4||*25uf, preamp cathode bypass.|
|C9||32uf, preamp main filter.|
|C10||50uf, preamp main filter (but 32uf always fitted in practice).|
|C14||8uf 150v, bias smoothing.|
* cathode bypass caps were TCC "Micropack"
So far no amp has come to light with 8uf and 50uf main preamp filter caps. The values were evidently simply carried over from the "AC80/100" schematic (and no AC80/100 has come to light with these values either).
Most of the grey panel AC80/100s have blue Hunts 25uf caps for the preamp valve cathode bypass (C3 and C4). The change to the light gold 25uf TCC "Micropack" seems to have taken place between serial numbers 392 and 420.
The Hunts factory, in contrast to Dubilier and TCC (both in North Acton), was in south London - Earlsfield, not too far from Wimbledon. The works formerly belonged to (and were originally built for) the Columbia Gramophone Company.
Pic. from the Britainfromabove website. Note in the foreground a vast array of allotments, the modern equivalent of medieval strip farming.
Extract from "The Economist" magazine, volume 216, July 10th, 1965:
Click for a larger image. The upper figure of "$10 million", a good eye-catching number, is echoed in the extract from Billboard magazine, below. To support the drive to export, the Burndept factory produced many more AC80/100s than Westrex had, and as outlined in yesterday's entry lower down on this page, a large number of "100W Amplifiers" in a comparatively short space of time.
What underlay the note in the Economist, however, was the deal done at the NAMM (National Association of Music Merchants) show at the Conrad Hilton in Chicago, June 27th - July 1st, 1965. The Thomas Organ Co. ordered $2-4 million worth of Vox equipment. "Billboard" magazine, again, records the higher figure.
Extracts from "Billboard" magazine:
July 31st, 1965 "BRITISH JENNINGS LANDS BIG ORDER": "An order for microphones, amplifiers and electronic organs worth four million dollars has been placed by the Thomas Organ Co. of America with the British firm of Jennings Musical Industries."
"The order is equal to four months production for J.M.I. and means the company is completely re-planning its production line at its factory in Dartford (Kent). Extra employess are being added."
"In the last six months J.M.I's export figures reached $10million - more than all the combined orders taken by the rest of Britain's musical instrument makers. The company has also had a record first year in the home market."
October 2nd, 1965: "Thomas Organ Co. president Joe Benaron flew here [London] for the closing days of the British Musical Industry's trade fair and talked with Jennings Musical Industry's executives about further marketing of Vox products in the U.S.A. He intends to 'boost the English sound throughout America'."
One of the topics that may have arisen on the occasion noted above was solid state amps. Dick Denney went out to Sepulveda in late October to assess work on the Super Beatle and other US models.
Another short note, this time on schematics and production. The schematic for the early fixed bias "100W Amplifier", below, is dated 30th May 1965.
Just under three weeks later, the "AC100/2 Amplifier" sheet was drawn up - on the 17th June. Eleven days after that, on the 28th June, the addition of the brimistor is recorded.
Around three hundred "100W Amplifiers" were produced at the Burndept works in Erith - serial numbers c. 430 - 730, all without the brimistor.
Although the dates given on the schematics are unlikely to correspond exactly with the start of production in the factory, the time lag between production and the drawing up of the schematics in these cases is not likely to have been great.
If we allow that production of the "100W Amplifier" lasted five or perhaps six weeks, approximately 10 per day must have rolled off the line.
The "100W Amplifier" schematic. Click for a larger image. The schematic is also on the main schematics page.
Early to mid 1965 was an intense period of activity for Vox/Burndept, particularly in view of the orders received from the Thomas Organ Co. in the States, the first being in September 1964 ($1m) and the second, mid '65 ($2-4m). Both were reported in "Beat Instrumental magazine.
A short note on the filter and cathode bypass capacitors in AC80/100s. At first these were light gold-coloured Dubiliers, presumably sourced direct from the Dubilier factory in North Acton (a short step from Willesden, where Westrex assembled the chassis for Vox).
The Dubilier Condenser Company, Ducon Works, North Acton - the complex in the upper centre of the picture is the Dubilier works. Image from the fab "Britain from Above" site.
In late 1964, however, Vox/Westrex seems to have bought in from TCC - the "Telegraph Condenser Company", also based in North Acton. The TCC capacitors were generally green "Micromite", printed in beautiful, heavy, Gill sans typeface.
One also finds in amps from late 1964 main filter capacitors (100uf, 500v) made by Daly Condensers of Ealing, West London (West Lodge Works, The Green, Ealing, W5).
But TCC and Daly were used only sparingly early on (generally in black panel amps). Dubiliers were the norm, and the company continued to supply Vox when production of the AC80/100 was moved from Westrex to Burndept Electronics (in Erith) in early 1965.
Green TCCs did become standard later on though with the advent of the fixed bias "100W Amplifier" in summer 1965.
A new quasi-database page type in development for galleries of images. Interim example here.
The display will scale with browser width. Single click popup image, single click close. Images are drag-and-droppable on a Mac.
To date the page has been tested on a PC with Chrome, Firefox, IE11 and IE12, and on Mac with Safari. If you encounter any bugs, let me know at this address.
30th May (long entry, scroll down)
From "Beat Instrumental" magazine no. 18, October 1964. The "Million Dollar" contract, signed around a month after the Beatles had completed their first large-scale tour of America.
[correction - the deal was signed at the British Music Trade Fair, which took place in late August while the Beatles were touring.
Few AC80/100s are likely to have gone to the States however before the spring of 1965. Westrex, which made the amp throughout 1964, was not geared up for volume production, and it evidently took some time to set the Burndept factory in Erith going, the first AC80/100s emerging from its line in March/April 1965.
The earliest dateable pictures to have come to light so far of US bands with AC80/100s are those of the Byrds and Paul Revere and the Raiders at the CBS promotional show in July of that year. See below (entry for 27th March).
Piece on Tom Jennings from "Beat Instrumental no. 19, November 1964.
"We first supplied The Beatles with Vox equipment three years ago and we are still doing so. When they went to America for the first time they did a show at the famous Hollywood Bowl and found that their 50 watt amps just couldn't pierce the screams of the audience, so, they asked us to produce something even more powerful. The results are their present 100 watt monsters."
"The Beatles' tours of the States created a terrific demand for our equipment and led to our contract with the Thomas Organ Company to supply them with five million dollars worth each year."
In relation to The Beatles in the USA, Jennings presumably meant 50 watt amps at the Washington Coliseum, not the Hollywood Bowl. "Five million dollars worth each year" probably encompasses a degree of hyperbole.
A gorgeous Jennings Electronic Industries AC40 and J50 speaker cab (2x12") pictured here. Thanks to Andreas for the pictures. The JEI pages as a whole will be updated and revamped soon.
The advert above first appeared in "Beat Instrumental" magazine, April 1964 - a promotional drive for the new AC80/100, assembled by Westrex for Vox in west London. The JMI catalogue in which the amp first appears - the image below - is from much the same date. The first pricelist known that mentions the amp is from May 1964.
New pictures of serial number 177 and its cab posted here.
Further pics of serial number 1111 now registered here.
A new page begun on Vox adverts in Beat Monthly magazine. The magazine, which became "Beat Instrumental" in late 1964, was aimed principally at musicians and bands and became the only publication in which Vox regularly advertised.
Recently sold on ebay, serial number 1111. Further pics posted here.
The Animals on stage in Copenhagen, 1st January 1966 - picture from the wonderful Getty Images archive (photographer: Jan Persson). The AC100 cab belongs however to The Tielman Brothers, whose drum-kit is visible far left.
A detail from the Brimar pricelist of 1966, showing the line for the CZ4 brimistor (as used in the AC100 Mark 2): 5/- (five shillings) in old money, equivalent to around £4 today. The list is available here.
The Byrds live on stage at a CBS Sales Conference on 5th July 1965, shortly after "Tambourine Man" went to number one in the U.S. All three guitarists are plugged in. The AC100s must, at this date, be cathode biased (AC80/100s). This is the earliest dateable picture that has come to light so far of an American band using, on stage in the USA, AC100 SDLs that did not belong to the Beatles or any other English band.
The equipment in the shot of the Byrds above was also used on that day by Paul Revere and the Raiders - see the pic. on the VoxShowroom site (though the amps are not AC100 Mark 2s as implied there). At a concert in Phoenix in 1965, date unknown, the Byrds had just the AC50 and two Foundation cabs - see this page.
As a side note, the only UK bands pictured with AC100 SDLs on stage in 1964 are the Beatles (of course), the Stones, Kinks and Yardbirds. The two last probably used the same amps.
A great shot from Getty Images of Mick Jagger leaning against the Stones' early AC100 SDL on stage at Olympia, Paris, 20th October 1964. The band had the amp in Belgium a few days earlier, but it is not seen on stage again after Paris.
Stones playing at the Amerikaans Theatre in Brussels on 18th October 1964. Photo by Hermann Selleslags.
Further pics of an early "100W Amplifier" added here.
Images of Jennings J100 (fully solid state) serial no. 1319 added on this page.
Further images of an amp with a serial number in the 1800s added here.
Serial number 1638, currently in Spain registered here.
Thanks to members of the BeatGear Cavern, the list of US Vox dealers has been corrected and augmented. See this thread. You will need to be a member of the BeatGear Cavern (free) to view the thread, however.
Pics of the chassis of an amp with a serial number in the 1800s added on this page.Thanks to Francesco for the pictures.
Page on Jennings PA100s updated.Thanks to Jan for pictures of serial no. 1015.
The list of Vox dealers in the USA now expanded Thanks to Charles Forssi for details on New York City and Florida. The advert for California, later to become a standard format, is said to have been issued on 23rd December 1964.
The page on Mullard EL34s now expanded.
A Brimar booklet on the brimistor added at the foot of this page.
New page on Mullard EL34s begun.
Serial number 2089 added on this page.
Some new Foundation Bass cabs added here.
There are now separate pages for the PA 50W and 100W amps.
New page on Vox and Woden Transformers added here.
The page on AC80/100s with black panels updated.
The page on AC80/100s made in late 1964 / early 1965 updated too.